KR100460256B1 - Silica refractory composition for filler - Google Patents

Abstract

The present invention relates to a silica-based refractory composition used in a filler for temporarily closing or opening a molten steel outlet, and its purpose is to increase the hole opening ratio and prevent erosion of the ladle-containing refractory material, thereby increasing the life of the refractory material. To this end, in the present invention, in the present invention, silica is the main component, and the basic oxide is coated on the surface of the silica, or the silica and the basic oxide are mixed and dispersed, or the carbon and the basic oxide are coated on the surface of the silica, and the chromium light is added thereto. The refractory composition for filler manufactured by mixing powder is provided.

Description

Silica refractory composition for filler

The present invention relates to silica-based refractory compositions, and more particularly to silica-based refractory compositions used in fillers to temporarily close or open the molten steel outlet.

In the steel industry or the non-ferrous industry, a filler containing a material in a hot molten state, for example, a facility such as a molten steel transport ladle, is temporarily closed or opened using a filler, and a silica-based refractory composition is used as a filler.

FIG. 1 is a cross-sectional view of a ladle in which a filler is installed, and FIG. 2A is a cross-sectional view enlarged around the filler in FIG. 1, and FIG. 2B is a cross-sectional view showing a state of opening the outlet in FIG. 2A. As shown in these drawings, when the filler (2) is put into the outlet of the lower ladle (1), the outlet is closed to receive the molten steel (3) of 1500 ° C or more in the ladle (1), the deoxidation or After the completion of the subsequent process, such as dewatering, when the nozzle immediately below the filler 2, that is, the sliding gate 4, is opened, the filler naturally flows down by the weight of the waste water, thereby opening the outlet port. will be.

The fillers that play such a role include firstly, a granular material having a particle size of 2.0 mm or less having a high purity of silica and having a fire resistance of about SK32 to SK35, and secondly, silica-chromium oxide containing tens of wt% of chromium oxide in the high purity silica. Materials such as the system are known.

The former silica material is mainly used in general steelmaking process. Especially, high purity silica material with a silica (SiO ₂ ) content of more than 95% by weight is used in processes requiring a higher hit ratio and higher porosity, and the latter silica-chromium oxide System materials are universal materials that are widely used in recent years.

Conventional fillers as described above have a problem in that the rate of spontaneous opening in the continuous steelmaking process, that is, the porosity of the hole, is not high enough as the granular materials mainly composed of silica or silica and chromium oxide.

In addition, a problem has been pointed out that erosion of the refractory material around the filler to cause a reduction in the life of the refractory material.

The present invention is to solve the problems as described above, the object is to increase the hole opening ratio and to prevent the erosion of the ladle embedded refractory material to increase the life of the refractory material.

Another object of the present invention is also to prepare fillers in an economical way.

1 is a cross-sectional view of a ladle in which a pillar is installed.

FIG. 2A is an enlarged cross-sectional view of the filler in FIG. 1;

FIG. 2B is a cross-sectional view illustrating a state in which a discharge port is opened in FIG. 2A.

3 is a state diagram of the MgO-SiO ₂ system.

4 is a state diagram of an MgO-Al ₂ O ₃ system.

5 is a cross-sectional view of the ladle showing that the silica-based refractory composition according to the present invention is used as a filler and installed in the ladle.

In order to achieve the above object, in the present invention, silica is the main component, and the basic oxide is coated on the surface of the silica, or the silica and the basic oxide are mixed and dispersed, or the surface of the silica is coated with carbon and the basic oxide. And it provides a refractory composition for the filler prepared by mixing the chromium light powder.

At this time, it is preferable to use 1 type or 2 types among CaO and MgO as basic oxide.

When the basic oxide is coated on the surface of the silica, it is preferable that one or two kinds of CaO and MgO are coated in the range of 2 to 20% by weight of CaO and MgO on the surface of the silica having a particle size of 2 mm or less and 80 to 98% by weight or less.

When mixing and dispersing the silica and the basic oxide, it is preferable to mix and disperse 2 to 20 wt% of one or two kinds of silica having a particle diameter of 2 mm or less and 80 to 98 wt% or less and CaO and MgO having a particle size of 1 mm or less. Do.

When carbon and basic oxides are coated on the surface of silica and the chromium ore powder is mixed therewith, on the surface of silica having a particle diameter of 2 mm or less, one or two of carbon having 0.2 to 1.5% by weight relative to silica, CaO and MgO It is preferable to coat | cover 0.1-0.5 weight% with respect to a silica, and mix 25-90 weight of 10-75 weight% of coated silica and the chromium light powder whose particle diameter is 1 mm or less.

Hereinafter, the silica refractory composition for filler according to the present invention will be described in detail.

In the present invention, silica is used as a main component. Silica has a low refractory degree at a melting point of about 1700 ° C. and has a high phase change, but is used as a main raw material of a filler because of its strong thermal shock characteristics. In the present invention, the filler is prepared in the following three forms by using silica as a main component, which is softened at a temperature around 1650 ° C. and has a certain fluidity.

First, a filler is prepared by coating basic oxides such as CaO, MgO, and the like on the surface of silica, or second, and adding and dispersing basic oxides, such as CaO, MgO, in which particle size is adjusted, to prepare a filler. Or, third, after coating carbon and basic oxide on silica, the filler is prepared by mixing chromium light powder on the coated silica.

When coating or adding CaO and MgO to silica or coating carbon and CaO and MgO to silica and then mixing the chromium ore powder, MgO-SiO ₂ based state diagrams of FIG. 3 and MgO-Al ₂ O ₃ As shown in FIG. 4, a trace amount of MgO and SiO ₂ react at a high temperature of 1400 ° C. or higher to induce the production of stable phase phosphite among silica particles, and is generated by a reaction as shown in Equation 1 below. CaO reacts with alumina (Al ₂ O ₃ ), which is a kind of steel inclusions, to form a CaO-Al ₂ O ₃ low melting point material to remove some inclusions, and to react with the alumina refractory in contact with the spinel and _{(Spinel, MgO-Al 2 O} 3) a may lead to corrosion inhibition of refractories by generating, has a new characteristic of the silica-based filler inhibits the under-grain silica illustrating a composite function, such as to reduce the factor of through holes poor It is. In FIG. 3, '22' is a pole sterite generation region, and in FIG. 4, '23' is a spinel generation region.

CaO and MgO have a very high melting point, which improves corrosion resistance, and is effective in degassing and removing inclusions. Thus, it is possible to effectively coat the silica-based refractory composition or to control the particle size to improve the function of the refractory composition. .

Hereinafter, each raw material used to prepare the silica-based refractory composition for filler according to the present invention will be described in detail.

In general, silica, which is a main raw material, is one obtained by pulverizing natural silica and having a particle size separated by a particle size of 2 mm or less, and a fine powder having a particle size of 0.5 mm or less is better, and a higher purity is better.

If the particle size of silica exceeds 2mm, the gap between particles increases, so that the molten water easily penetrates, which is a direct cause of the pore defect. If the fine powder with a particle diameter of 0.5mm or less increases, the sintered layer is densely sintered, which also causes the pore defect. Becomes

In addition, silica is required to have extremely good fluidity, so when handling molten metal with very low viscosity, such as molten stainless steel, the maximum particle size is 1.5mm or 1mm depending on the conditions of use. You can also get

CaO is preferably used in the form of quicklime (CaO) or limestone (CaCO ₃ ), and MgO is preferably used in the form of magnesium hydroxide (Mg (OH) ₂ ) or magnesium oxide (MgO), and when heated with MgCO ₃ You may use the raw material which MgO produces | generates.

In the case of coating CaO and MgO on silica, fine powdery materials are coated with silica particles using a coating apparatus such as a kneading machine in a liquid phase in which an adhesive is dispersed together with water. One or two of CaO and MgO are coated. It is preferable to coat so as to be 2 to 20% by weight.

In this case, when the coating amount of CaO and MgO is less than 2% by weight, it is less than the desired effect, that is, it does not show the effect of the opening and closing of the molten steel, the degassing effect and the inhibition of refractory erosion. Problems such as the generation of excess low melting point oxide below 1400 ℃ than the production of ₂ O ₃ and SiO ₂ -MgO-based product is accelerated rather than refractory erosion. Therefore, 2 to 20% by weight of the two species of CaO and MgO is preferable, and more preferably, 7 to 10% by weight is most effective.

In order to improve the coating property, a binder may be used, and any binder may be used as long as it is a conventional water-soluble organic binder, and may be any kind such as PVA, PVB, and CMC. Good for you. The coating amount is increased as the amount of the binder added up to 1% by weight. However, the coating cost is increased when the amount of the binder is increased by more than 1% by weight. Therefore, the amount of the binder is preferably 1% by weight or less.

When CaO and MgO are added and mixed in granules without coating, it is better to add one or two of CaO and MgO at a maximum particle diameter of 1 mm or less at 2 to 20% by weight as a granule having a smaller size than silica. It should not be impeded by the fluidity of

In this case, since the particle size of the basic oxide has a sensitive influence on the performance of the silica-based refractory composition, adjustment of the particle size is very important. It is preferable that the particle size of the basic oxide is usually half or less of silica, that is, 1 mm or less. When the particle size of the basic oxide is larger than 1 mm, the contact area with silica or internal refractories becomes small, so that the desired function is difficult to be exhibited, and a smaller amount of fine powder is more effective.

The use method of the basic oxide mentioned above is the same also about the silica type composition containing chromium oxide.

In addition, in the silica-based or chromium oxide-containing silica-based composition, at a high temperature of about 1650 ° C., the refractory composition of the high temperature contact part softens to a certain degree so that it is easily collapsed during natural opening and easily discharged to the lower part. It is also possible to add feldspar fines.

Feldspar adds 0.1-1 weight% of particle diameters 0.5 mm or less. If the amount of feldspar is less than 0.1% by weight, it is not possible to obtain a uniform coating effect. If the amount of feldspar is more than 1%, the amount of feldspar added increases from 0.1 to 1% by weight. It is preferable.

On the other hand, in the case of coating graphite or amorphous carbon having a high carbon content on silica, graphite with an adhesive such as PVA, CMC, phenol, or an inorganic adhesive such as sodium silicate in an aqueous or aqueous solution having excellent dispersibility of aqueous or carbon However, the amorphous carbon is dispersed and coated, and the carbon content is preferably at least 0.2% by weight and at most 1.5% by weight based on silica. At this time, the amount of the solution, such as water or thinner does not need to be limited separately, it does not matter as long as the carbon coating workability is good for silica.

When coating a carbon-based material on silica, a small amount of ultrafine basic oxides of limestone or magnesia dispersed in several microns can be added to increase the performance of the desired silica composition. Limestone and magnesia It is effective to add at least 0.1% by weight and at most 0.5% by weight as species. At this time, limestone or magnesia may be used as long as it is the same kind of material containing CaO and MgO.

If the amount of carbon used to coat the silica particles is less than 0.2% by weight, the effect of the desired under-sintering of silica is insufficient. If the amount of carbon exceeds 1.5% by weight, the amount of fine carbon particles on the surface of the silica becomes excessive. It takes a lot of work time and a large amount of carbon is eliminated during handling, which may cause problems during the manufacturing process or during use. In actual use, the softening of silica particles on the surface may cause poor pore size.

When the basic oxide added with carbon is less than 0.1% by weight, the adhesion of carbon to silica particles is poor and the effect of suppressing refractory erosion is insufficient. If the content exceeds 0.5% by weight, the porosity is reduced.

In the case of coating the carbonaceous material or the basic oxide as described above, when the coated silica is mixed with at least 10% by weight up to 75% by weight and with chromium light powder at least 25% by weight up to 90% by weight, the desired porosity improvement effect is achieved. If it is out of this range, the thickness of the surface softening layer is increased or the porosity due to penetration of molten steel is inferior in use.

As described above, when the basic oxide is coated or dispersed on the silica or chromium oxide-containing silica refractory composition, or the carbon and the basic oxide are coated on the silica and then mixed with the chromium light powder, as shown in FIG. CaO and MgO coated or added to the silica particles or chromium oxide particles are formed with the surface softening layer 12 until the silica 11 of the microcrystalline layer falls down due to the self-weight of the upper molten steel and immediately before the passage of the lower part is opened. Thin dense sintering of Fosterite (Forsterite, 2MgOSiO ₂ ) or Spinel (MgO-Al ₂ O ₃ ) on the refractory surface of the ladle 21 while maintaining a unique structure composed of the sintered layer 13 Layer 14 is formed.

These sintered layers 13 and 14 do not show continuous improvement of corrosion resistance, but have sufficient effects to temporarily improve the porosity and suppress refractory erosion.

Hereinafter, the silica-based refractory composition for filler according to the present invention will be described in more detail with reference to the following examples.

Examples 1-8

In Examples 1 to 8, a silica-based refractory composition was prepared by the composition shown in Table 1, wherein silica was used as the particle size separated by 2 mm or less of natural silica powder having a SiO ₂ of 97% or more. A powder having a particle size of 2 mm or less was used, and a feldspar was used with a powder having a particle size of 0.5 mm or less.

After contacting the molten steel at 1650 ° C. for 60 minutes using the silica-based refractory composition according to Examples 1 to 8, the thickness of the surface softening layer on the upper part of the filler, the thickness of the reaction sintering layer below the ladle, and the ladle refractory material The thickness of the refractory reaction layer, which is a sintered layer between the composition and the composition, was measured, and the porosity of the molten steel at 1650 ° C. was measured, and the results are shown in Table 1.

In Comparative Examples 1 to 6, the silica-based refractory composition was prepared with a composition outside the scope of the present invention, and the thickness of the surface softening layer, the reaction sintering layer, the refractory reaction layer, and the porosity were measured in the same manner as in Example. The results are shown in Table 1 together.

Unit: weight% division Example Comparative example One 2 3 4 5 6 7 8 One 2 3 4 5 6 Silica 98 91 60 82 60 79 62 94 98.1 58 83.1 79 98.1 49 CaO (limestone) 2 8 20 3 4 1.9 21 0.7 10 MgO (magnesia) 2 10 20 5 2 1.2 11 1.9 21 Chrome 20 15 30 30 10 20 15 30 feldspar One One One One Binder 0.5 0.5 0.5 0.5 0.5 Surface Softening Layer 18 17 15 17 16 16 15 18 18 14 16 16 18 16 Reaction layer 7 7 6 7 6 6 6 7 7 5 6 6 7 5 Refractory reaction layer 1.5 2.6 2.5 1.5 2.8 3.2 3.1 3.1 1.3 2.2 1.2 3.5 1.3 2.7 Opening success rate 99 98 97 98 97 97 99 99 96 94 97 96 96 93

As shown in Table 1, in Comparative Examples 1, 3, and 5, the content of CaO and MgO is too small to produce a refractory reaction layer, which did not show a higher refractory erosion inhibitory effect than the conventional composition.

When the amount of CaO and MgO is excessive as in Comparative Examples 2, 4 and 6, the effect of the reaction sintering layer under the surface softening layer directly below the surface of the composition is too small or the thickness of the refractory reaction layer is too small. In the case of the excessive Comparative Example 6 showed that the porosity also drops sharply.

Examples 9-16

In Examples 9 to 16, carbon black and CaO or MgO were coated on the silica particles with the composition shown in Table 2, and then chromium ore powder was mixed thereto to prepare a silica-based refractory composition for the filler. In the composition of Table 2, the marks in parentheses indicate the weight ratio to the silica particles. In this case, silica was used to separate the natural silica powder having a SiO ₂ ratio of 97% or more with a particle size of 1 mm or less, and chrome ore used a powder having a particle size of 1 mm or less.

The prepared silica-based refractory composition was contacted with molten steel at 1650 ° C. for 60 minutes using the filler of the ladle, followed by the surface softening layer thickness and the upper middle sintered layer thickness of the filler, and the sintered layer between the ladle refractory and the composition. The thickness of the reaction layer was measured, and the porosity was measured for molten steel at 1650 ° C. The results are shown in Table 2.

In Comparative Examples 7 to 12, as shown in Table 3, silica-based refractory compositions were prepared in a composition outside the scope of the present invention, and used as a filler to prepare the surface softening layer, the reaction sintering layer, and the refractory reaction layer in the same manner as in Example. The thickness and porosity were measured.

Unit: weight% division Example 9 10 11 12 13 14 15 16 Silica 10 20 25 30 35 40 60 75 CaO (limestone) (0.1) (0.1) (0.3) (0.2) (0.5) MgO (magnesia) (0.1) (0.1) (0.3) (0.1) (0.5) Chrome 90 80 75 70 65 60 40 25 Carbon black (carbon) (0.2) (0.5) (0.5) (0.5) (0.7) (1.0) (1.0) (1.5) Binder (0.5) (1.2) (1.5) (1.5) (2.0) (2.0) (2.5) (3.0) Surface Softening Layer 8 10 10 12 14 14 15 15 Reaction layer 5 6 7 7 6 7 7 7 Refractory reaction layer 1.2 1.5 2.0 3.3 2.9 2.0 2.5 2.5 Opening success rate 99 99 100 100 99 99 98 97

Unit: weight% division Comparative example 7 8 9 10 11 12 Silica 9 15 40 50 50 76 CaO (limestone) (0.3) (0.6) MgO (magnesia) (0.3) (0.6) (0.2) Chrome 91 85 60 50 50 24 Carbon black (carbon) (0.4) (0.1) (0.2) (1.6) (0.1) Binder (1.2) (0.3) (0.5) (3.2) (0.3) (0.4) Surface Softening Layer 9 10 15 15 16 16 Reaction layer 5 5 7 7 6 8 Refractory reaction layer 3.5 3.1 2.2 2.2 3.2 3.4 Opening success rate 94 96 96 93 96 94

As shown in Table 2, Examples 9 to 16 showed an average porosity of 99% or more.

On the other hand, as shown in Table 3, Comparative Examples 7 to 12 did not show the desired porosity. In particular, as in Comparative Example 7, when the content of silica is less than 10% by weight and the amount of the basic floor oxide added is more than 0.5% by weight, the reaction sintered layer is too small and the porosity deteriorates rapidly.

In addition, as in Comparative Example 14, when the content of silica is more than 75% by weight and the powdered chromium ore is less than 25% by weight, or when the carbon content is excessive, such as 10, the surface softening layer and the reaction sintering layer Due to the thickening of the porosity worsens, it can also be the cause of impossibility.

The silica-based refractory composition for filler according to the present invention includes CaO and MgO to remove non-metallic inclusions in the molten steel in the ladle and exhibits a deflow effect.

In addition, when the silica-based refractory composition according to the present invention is used as a filler, a sintered layer is formed on the top of the microcrystalline silica, which is under the surface softening layer of the filler, thereby improving the porosity.

In addition, the ladle refractories and the composition reacts to form a dense sintered layer on the surface of the refractory, thereby temporarily inhibiting the erosion of the refractory surrounding the outlet in the ladle, thereby extending the life of the refractory. It is effective in improving stability and reducing costs.

Claims (7)

delete delete delete delete In the silica-based refractory composition used in the filler (opener) for opening and closing the molten steel outlet of the steelmaking ladle (ladle), 80 to 98% by weight of silica having a particle diameter of greater than 0 and less than or equal to 2 mm, one or two of 2 to 20% by weight of CaO and MgO, and one or two of CaO and MgO to the surface of the silica. A silica-based refractory composition, characterized in that it comprises an amount of less than or equal to 1 wt% of the binder by extrapolation. In the silica-based refractory composition used in the filler (opener) for opening and closing the molten steel outlet of the steelmaking ladle (ladle), 80 to 98% by weight of silica having a particle diameter of greater than 0 and less than or equal to 2 mm, one or two of 2 to 20% by weight of CaO and MgO, and one or two of CaO and MgO to the surface of the silica. Silica-based fire-resistant composition, characterized in that it comprises 0.1 to 1% by weight of feldspar coated on the, and the particle size is greater than 0 and less than or equal to 0.5 mm. In the silica-based refractory composition used in the filler (opener) for opening and closing the molten steel outlet of the steelmaking ladle (ladle), 80 to 98% by weight of silica having a particle diameter of greater than 0 and less than or equal to 2 mm, 1 or 2 to 20% by weight of CaO and MgO, and 1 or 2 and carbon to CaO and MgO. Coated on the surface of silica, the carbon is 0.2 to 1.5% by weight extrapolated to the silica, The silica-based refractory composition is 70 to 75% by weight of the coated silica, 25 to 30% by weight of the chromium ore powder is greater than 0 and less than or equal to 1 mm.