KR101739277B1 - Method for refining stainless steel in converter with decreasing corrosion of refractory in converter - Google Patents

Abstract

Disclosed is a method for refining stainless steel in a converter with decreasing corrosion of a refractory in the converter. According to an embodiment of the present invention, the method for refining stainless steel in the converter comprises: a step of charging molten iron to the converter; a decarbonizing step; and a reducing step. Moreover, slag formed in the decarbonizing step is MgO-SiO_2-based slag. Therefore, the MgO-SiO_2-based slag is generated to reduce a slag amount, and an elution amount of a refractory can be reduced. An input of a base material is reduced for production costs to be reduced.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method of refining stainless steels having reduced refractory erosion of a converter,

The present invention relates to a method of refining a stainless steel having reduced refractory erosion of a converter, more specifically, by reducing the amount of slag to greatly reduce the amount of leached refractories, the refractory erosion can be reduced to improve the life of the refractory, To a method for refining a converter of a stainless steel in which refractory erosion of a converter is reduced, which can significantly reduce the amount of the additive and the amount of the reducing agent used.

The production method of stainless steel can be largely divided into a manufacturing method using scrap and a manufacturing method using molten iron according to the raw material to be used. Compared to scrap raw material production methods which depend heavily on scrap and raw material costs, manufacturing methods using charcoal are considerably advantageous in terms of cost, and in recent years, major stainless steel manufacturers around the world are also using charcoal manufacturing methods .

Generally, stainless steel manufacturing method using scrap is performed by dissolving scrap containing most essential elements of stainless steel such as chrome in an electric furnace and then decarburizing it in a refining furnace. In the manufacturing method using molten iron, a decarburization process is performed after a pretreatment for removing impurities such as silicon and phosphorus from a molten iron from a blast furnace, and a decarburization process is carried out. In most cases, There are many cases where a decanter of stainless steel is also carried out using a converter because it also has a converter.

1 is a graph for explaining the composition of slag generated during the steelmaking refining operation of stainless steel. 2 is a flowchart of a conventional stainless steel refining operation.

As shown in FIG. 2, the conventional stainless steel refining operation includes a decarburization step 20 in which a molten iron charging step 10, a subsidiary material and a temperature increasing material are charged into a converter and oxygen is blown, a reducing step 30 And a step 40 of pouring molten steel into the ladle. In this case, prior to the decarburization step (20), quicklime and light dolomite were used as sub-materials.

In case of CaO-SiO ₂ slag as shown in FIG. 1, CaO / SiO ₂ ratio should be theoretically 1.5 or more in order to prevent elution of MgO refractory at 1,700 ° C. At this time, if the fluorspar is used or the temperature is higher, the ratio should rise. In practice, the ratio of CaO / SiO _{2 is} almost close to 2, and thus the amount of slag is increased, thereby increasing the amount of leached refractories.

Korean Patent Publication No. 10-1997-0027321

The embodiments of the present invention can reduce the amount of slag to greatly reduce the amount of refractory leaching and thereby improve the life of the refractory by reducing the erosion of the refractory and improve the life of the refractory by reducing the consumption amount of the reducing agent, And to provide a method for refining the reduced stainless steel.

A method for refining a stainless steel having reduced refractory erosion of a converter according to an embodiment of the present invention includes charging a charcoal to a converter, a decarburization step and a reducing step, wherein the slag formed in the decarburization step is MgO-SiO ₂ series slag.

According to an embodiment of the present invention, the converter may include a refractory material including at least one selected from the group consisting of MgO-based and MgO-C-based materials.

According to an embodiment of the present invention, the MgO / SiO ₂ ratio of the slag may be 1.2 to 1.9.

According to an embodiment of the present invention, in order to form the MgO-SiO ₂ -based slag, it may include a step of adding a sub ingredient including at least one selected from the group consisting of MgO and MgO-C .

According to an embodiment of the present invention, the MgO-based additive may include at least one selected from the group consisting of brucite and spent brick.

Also, according to an embodiment of the present invention, the MgO-C based additive may be a spent refractory.

According to an embodiment of the present invention, the method may further include the step of injecting a heating material containing at least one selected from the group consisting of coke and a carbonaceous material for heating the molten iron.

Also, according to an embodiment of the present invention, when the MgO-C based subordinate material is charged, the amount of the heating material to be charged can be determined based on the C content contained in the MgO-C based subordinate material when the heating material is charged.

In the embodiments of the present invention, CaO-SiO ₂ slag is prevented from being generated by using all of the MgO or MgO-C based additives in the case of using quicklime and hard dolomite as auxiliary materials in the stainless steel steelmaking operation, and MgO-SiO ₂ The amount of slag can be reduced and the amount of refractory leaching can be reduced accordingly.

Further, it is advantageous in terms of securing the temperature of the molten steel because the amount of the additive material for slag formation is reduced and the cost can be reduced as well as the heat loss. When the MgO-C additive is used as the additive, the additional amount of the additive It is possible to reduce the cost.

1 is a graph for explaining the composition of slag generated during the steelmaking refining operation of stainless steel.
2 is a flowchart of a conventional stainless steel refining operation.
3 is a flowchart of a stainless steel refining operation 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. The following embodiments are provided to fully convey the spirit of the present invention to a person having ordinary skill in the art to which the present invention belongs. The present invention is not limited to the embodiments shown herein but may be embodied in other forms. For the sake of clarity, the drawings are not drawn to scale, and the size of the elements may be slightly exaggerated to facilitate understanding.

3 is a flowchart of a stainless steel refining operation according to an embodiment of the present invention.

Referring to FIG. 3, a refining method of a stainless steel in which refractory erosion of a converter is reduced according to an embodiment of the present invention includes a charging step 10, a decarburization step 25, a reducing step 30, And pouring molten steel into the ladle. The slag formed in the decarburization step (25) is MgO-SiO ₂ slag.

In the present invention, all of the MgO or MgO-C based additives were used in the decarburization step (25) for improving the slag, in which quicklime and light dolomite were used as the conventional additives. Accordingly, CaO-SiO ₂ slag is conventionally generated, whereas MgO-SiO ₂ slag is generated in the present invention.

Referring to FIG. 1, in order to prevent elution of MgO-based refractory at 1,700 ° C. in the case of CaO-SiO ₂ -based slag, CaO / SiO ₂ The ratio should be at least 1.5. At this time, when fluorite is used or when the temperature is higher, the ratio is further increased. In actual practice, CaO / SiO ₂ The ratio is used close to two.

On the other hand, in case of MgO-SiO ₂ system, MgO / SiO ₂ ratio of 0.8 or more can inhibit MgO refractory leaching. However, the MgO / SiO ₂ ratio actually needs to be higher in practical use. However, a small amount of MgO is still required. In other words, for the same amount of Si to be charged, CaO needs to be charged 1.5 times the theoretical amount, but MgO requires only 0.8 times, so that the actual input amount is greatly reduced.

That is, since the amount of the sub-raw material for slag formation is greatly reduced due to the decrease in the amount of slag, the cost can be reduced. In addition, since the amount of the sub-raw material is small, the heat loss is reduced in terms of heat, which is much advantageous in terms of securing the temperature of the molten steel. Accordingly, the amount of the gaseous material for heating can be reduced later, The scrap can be further dissolved.

For example, the converter may include a refractory material including at least one selected from the group consisting of MgO-based materials and MgO-C-based materials.

Referring to Figure 2, to form CaO-SiO ₂ based slag to the decarburization step 20 using calcium oxide and gyeongso dolomite with additives, to the interior of the converter includes an MgO-based or MgO-C based refractory CaO-SiO ₂ In the case of the slag, the solubility of MgO is about 10%, and the MgO of the refractory is eluted into the slag, thereby causing the erosion of the refractory.

However, in the case of the MgO-SiO ₂ slag, since the MgO is already saturated in the slag, erosion of the refractory can be prevented. For example, in the case of a dolomite (MgO-CaO) refractory containing MgO, the CaO is eluted and the slag becomes the same as the CaO-SiO ₂ slag, causing problems such as erosion of the refractory, Is preferably an MgO-based or MgO-C-based refractory.

Therefore, when the slag generated in the electrolytic refining process is MgO-SiO ₂ -based slag, the amount of slag is greatly reduced.

For example, the MgO / SiO ₂ ratio of the slag may be 1.2 to 1.9.

When the MgO / SiO ₂ ratio of the slag is less than 1.2, MgO in the refractory material is eluted into the slag when the ratio of MgO / SiO ₂ is relatively low, thereby increasing the amount of the refractory loss. When the MgO / SiO ₂ ratio of the slag is more than 1.9, the slag fluidity is lowered, and the reducing property of Cr ₂ O ₃ relatively decreases.

In the decarburization step, and a step to input the one or more additives selected from MgO and MgO-C-based group of to step to form the MgO-SiO ₂ based slag on the molten iron. Thereafter, a step of injecting a heating material containing at least one selected from the group consisting of coke and a carbonaceous material for heating the molten iron after the addition of the subsidiary material or the addition of the subsidiary material is carried out.

For example, the MgO-based additive may include, but is not limited to, any one or more selected from the group consisting of brucite and spent brick, .

For example, the MgO-C additive may be a spent refractory, but not limited thereto, as long as it can provide MgO-C. The above-mentioned waste refractory is used as a refractory, and its life is over, and its composition is about 75% MgO-15% C. It is not only cheaper but also includes C, which is very advantageous in terms of economy. At this time, the C content of the waste refractory material is not limited because the amount of the heating material can be controlled later.

The amount of the heating material may be determined based on the amount of C contained in the MgO-C based additive material when the MgO-C based additives are added in the step of adding the additives.

That is, when the MgO-C based subordinate material is charged, the amount of C charged in the heating material, for example, the amount of the carbonized material is measured by measuring the content of C contained in the subordinate material, Can be input. Therefore, when C is added to the MgO system as an additive in the present invention, there is an advantage that addition of the additional carbon powder can be reduced.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example  And Comparative Example

The molten iron dissolved in the initial induction melting furnace was charged to a decarburization furnace, and then an additive material was added to the decarburization furnace in accordance with the conditions of Examples 1 to 3 and Comparative Examples 1 to 5 shown in Table 1 below. And decarburization was carried out by controlling CaO / SiO ₂ and MgO / SiO ₂ to prepare stainless steel.

Supplementary material CaO / SiO ₂ MgO / SiO ₂ Refractory weight (kg / ch.) Cr percent yield (%) Example 1 Lung lobe - 1.2 185 94.2 Example 2 Lung lobe - 1.9 160 94.3 Example 3 Lung lobe - 1.6 170 94.6 Comparative Example 1 Quicklime and light dolomite 1.9 - 290 94.7 Comparative Example 2 Quicklime and light dolomite 2.0 - 260 94.6 Comparative Example 3 Quicklime and light dolomite - 0.9 220 94.2 Comparative Example 4 Quicklime and light dolomite - 2.0 170 92.3 Comparative Example 5 Quicklime and light dolomite - 1.1 210 94.1

In Table 1, the amount of refractory loss refers to the amount of MgO eluted from the refractory when the refining operation is performed once (ch.), And the Cr real water rate is calculated by subtracting the amount of Cr lost to slag Cr ratio. The amount of the refuse hand was measured by setting the charge (ch) until charging the charcoal.

That is, the high melting point means that the refractory deterioration rate is high because the refractory loss rate is high, and the Cr real water rate is low, which means that the amount of Cr oxide lost by the slag is large and the manufacturing cost is increased.

Referring to Table 1, when the CaO-SiO ₂ slag is formed by using the existing burnt lime and the light dolomite as in the comparative example, it can be seen that the refractory loss is as high as 260 to 290 kg / ch. On the other hand, it can be seen that when the MgO-SiO ₂ slag is formed by using the pulverized coal as in the embodiment, the amount of the refractory loss is remarkably reduced to 160 to 185 kg.

However, even in the case of the same MgO-SiO ₂ slag, when the MgO / SiO ₂ ratio is less than 1.2, the melt loss is 200 kg / Which is higher than the above-mentioned value. This means that the MgO / SiO ₂ ratio is relatively low, and MgO in the refractory is eluted into the slag.

When the ratio of MgO / SiO ₂ is more than 1.9, the amount of Cr is decreased, but the Cr realization rate is lowered. For example, when the MgO / SiO ₂ ratio is 2.0, the Cr realization rate is 92.3%. This is because the slag fluidity is poor and the Cr ₂ O ₃ reducing property is relatively hot.

Therefore, the MgO-SiO ₂ slag compared to the conventional CaO-SiO ₂ slag is effective in improving the lifetime due to the low melting point of the refractory. However, controlling the MgO / SiO ₂ ratio to 1.2 ~ This is also important in securing the rate of error. The above results are derived from steelmaking temperatures in the range of 1,600 to 1,800 ° C.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited thereto. Those skilled in the art will readily obviate modifications and variations within the spirit and scope of the appended claims. It will be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention.

10: Charging line charging step 20, 25: Decarburization step
30: reduction step 40: molten steel laden step

Claims (8)

1. A method for refining stainless steel by charging a charcoal in a converter, a decarburization step and a reducing step,
Wherein the converter includes a refractory material including at least one selected from the group consisting of MgO-based and MgO-C-based materials,
The slag formed in the decarburization step is a MgO-SiO ₂ slag,
Wherein the slag has a MgO / SiO ₂ ratio of 1.2 to 1.9, wherein refractory erosion of the converter is reduced. delete delete The method according to claim 1,
The MgO-SiO ₂ system to form a slag with a MgO-based, and MgO-C to step refractory erosion of the converter characterized in that it comprises the step of inject additives includes at least one selected from the group consisting of reduction of stainless steel Converter refining method. 5. The method of claim 4,
Wherein the MgO-based additive comprises at least one selected from the group consisting of brucite and spent brick. 6. The method of claim 1, wherein the MgO-based additive is selected from the group consisting of brucite and spent brick. 5. The method of claim 4,
Wherein the MgO-C based additive is a spent refractory. The method of claim 1, wherein the MgO-C based additive is spent refractory. 5. The method of claim 4,
The method of claim 1, further comprising the step of injecting a heating material containing at least one selected from the group consisting of coke and gaseous materials to raise the temperature of the molten iron. 8. The method of claim 7,
When the MgO-C based additive is charged,
Wherein the charging amount of the heating material is determined based on the C content contained in the MgO-C based subsidiary material when the heating material is charged.

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