KR100591715B1 - Refractories for sliding gate plate - Google Patents

Abstract

 The present invention is to optimize the microstructure according to the use of ultra-fine particle size in the composition of the raw material, and to control the composition and particle size of the raw material to prevent the loss of carbon due to dissolution and oxidation in molten steel during use and the deterioration of strength during use. The present invention relates to a sliding fireproof material having an improved service life compared to its product.

According to the configuration, 20 to 60 parts by weight of sintered (or electrolytic) alumina having a particle size of 1 to 3 mm, 15 to 45 parts by weight of sintered (or electrolytic) alumina having a particle size of 1 to 0.04 mm, sintered (or electrolytic) zirconia-mullite 5-25 weight part, 5-25 weight part of sintered (or electrolytic) zirconia-alumina, 3-13 weight part of plastic aluminas, 0.5-5 weight part of Si fine powders, 1-5 weight part of carbon, alumina, silica, alumina-mer 3 to 10 parts by weight having one or more selected 20 to 900 nm (nanoparticles) selected from light and alumina-zirconia, and 0.3 to 5 parts by weight of an antioxidant.

Sliding plate fireproof material. Zirconia-Mullite. Nanoparticles

Description

Refractories for sliding gate plate}

1 is a cross-sectional view showing a sliding plate structure

Figure 2a is a micrograph showing a conventional microstructure

Figure 2b is a state diagram showing the appearance of the product after use as a conventional product

Figure 3a is a micrograph showing the microstructure of the present invention

Figure 3b is a state diagram showing the appearance of the product after use as a product of the present invention

Explanation of symbols for main parts of the drawings

1: upper nozzle 2: lower nozzle 3: upper sliding plate

4: lower sliding plate

The present invention relates to a sliding plate for controlling the flow of molten metal, and more particularly to the molten steel and non-metal oxide by improving the strength and chemical resistance to the microstructure according to the application of ultra-fine nanoparticle raw material It relates to a sliding plate suitable for minimizing wear of the bore or stroke due to hand, thermal shock and oxidation resistance.

Ladle and tundish under the steelmaking industry is equipped with a sliding plate for controlling the discharge of molten steel and its discharge.

1 is a cross-sectional view showing a sliding plate structure, in which an upper nozzle 1 and a lower nozzle 2 are mounted, and an upper sliding plate 3 and a lower sliding plate 4 made of a refractory material are installed therebetween.

The life of the sliding plate is determined by the increase in the number of times of use, the increase in casting time and the number of operation injections, oxygen washing after casting, steel grade, etc., these refractory material is a mecca equipped with cracks due to thermal shock of the casting and the present refractory material In addition, cracking occurs due to deviation of restraint stress depending on the flatness of ladle or tundish.

The cracks may cause inflow of nitrogen or oxygen into the molten steel to degrade the quality of the molten steel, and may cause a drop of the sliding plate refractory material during use, which may cause problems of molten steel during steelmaking and continuous casting operation. In addition, wear and tear caused by molten steel, non-metal oxide melting, oxidation and deterioration occur. This phenomenon is that the added carbon is removed by oxidation during use to improve the solvent content, thereby weakening the tissue binding force by these components. Tissue deterioration such as porosity and adhesion by nonmetal oxides can be accelerated, leading to a problem in which a part of the refractory material of the sliding portion is melted as shown in FIG. 2B.

As a member for improving the above problems, in Korean Patent Publication No. 90-0044751, alumina 50 to 90% by weight, Al ₂ O ₃ -SiO ₂ system, Al ₂ O ₃ -ZrO ₂ system, Al ₂ O ₃ -SiO _2- Refractory materials for sliding nozzles composed of at least one selected from ZrO ₂ and up to 30% by weight, carbon 3 to 8% by weight, and Si have been proposed, but the service life is limited due to the deterioration of the structure during use due to the lack of bonding between particles. have.

On the other hand, Japanese Patent Application Laid-Open No. 58-125660 is known, including Korean Patent Publication No. 10-0384619, but none of them can achieve satisfactory results in strength and content.

 The present invention is to improve the above-mentioned conventional problems, in the composition of the raw material causing the limit of the multi-use life, the use of carbon by optimizing the microstructure according to the use of ultra-fine particle size and adjusting the composition and particle size of the raw material The purpose of the present invention is to obtain a sliding refractory material having improved properties compared to existing products, due to the loss problem due to dissolution and oxidation in molten steel and the deterioration of strength during use.

The present invention for achieving the above object is 20 to 60 parts by weight of sintered or molten alumina having a particle size of 1 to 3 mm, 15 to 45 parts by weight of sintered or molten alumina having a particle size of 1 to 0.04 mm, sintered (or molten) zirconia-mul 5 to 25 parts by weight of light, 5 to 25 parts by weight of sintered (or electrolytic) zirconia-alumina, 3 to 13 parts by weight of plastic alumina, 0.5 to 5 parts by weight of Si fine powder, 1 to 5 parts by weight of carbon, alumina, silica, alumina At least one selected from mullite and alumina-zirconia is composed of a sliding plate refractory material composed of 3 to 10 parts by weight having 20 to 900 nm (nanoparticles) and 0.3 to 5 parts by weight of an antioxidant.

In addition, the present invention is 5 to 25 parts by weight of the sintered (or molten) zirconia-mullite, 5 to 50 parts by weight instead of 5 to 25 parts by weight of sintered (or molten) zirconia-alumina or One or two selected from 5 to 50 parts by weight of sintered (or electrolytic) alumina-zirconia can be used.

In the above composition, the alumina improves the solvent resistance and spalling resistance properties by varying the particle size distribution, and by appropriately mixing the amount of the alumina. If the amount is too large, the spalling resistance is lowered. Is less.

In the present invention, since the alumina mineral alone is not enough to improve heat spalling resistance and solvent resistance, sintered (or electrolytic) alumina-zirconia raw material or sintered (or electrolytic) zirconia-mullite raw material is added. There is little effect, and the said effect cannot be anticipated below a lower limit.

In the sintered (or molten) zirconia-mullite raw material, zirconia crystals exist to precipitate inside and around the mullite crystals to protect the mullite crystals, thereby having corrosion resistance and lowering the coefficient of thermal expansion.

In addition, the present invention preferably uses a plastic alumina of less than 1㎛ by improving the microstructure to increase the mechanical strength and chemical resistance. Therefore, above the upper limit may cause a molding failure during manufacturing, and below the lower limit, the improvement of the microstructure of the product is not made, and the improvement in the contents is weak.

In addition, the present invention is to increase the bonding strength of the product, and to improve the thermal shock resistance of the metal silicon (Si) is less than 3 parts by weight of the solvent content, and less than 1 part by weight of the silicon carbide produced during the reaction sintering and carbon Thermal shock resistance does not improve, such as insufficient strength due to lack of absolute amount.

Carbon (C) is for improving the thermal shock resistance and the solvent resistance, it is in the range of 1 to 5 parts by weight. At this time, the degradation of the tissue due to oxidation occurs above the upper limit, and the improvement of the thermal shock resistance and the contents decreases below the lower limit such as insufficient strength expression due to reaction with silicon and insufficient corrosion resistance characteristic of carbon.

Carbon is added in addition to the impregnation, and the mineral forms the amorphous (carbon black, anthracite, etc.) or crystalline (graphite) particles. Particles of about 0.2 mm or less can be applied.

On the other hand, the oxidation and deterioration of the sliding plate is weakened due to the oxidation of the carbon added in the sliding plate due to oxidation during use, the weakening of the tissue binding force by these components, the pore phenomenon is easy to attach by molten steel and non-metal oxides In order to improve the phenomenon in which a part of the refractory material part of the sliding part is melted, an antioxidant capable of preventing oxidation at low and high temperatures is used.

The antioxidant used at this time may be various carbides (e.g. SiC, ZrC, B ₄ C, Al ₄ C _3, etc.), borides (e.g. ZrB ₂ , CaB ₆ , MgB, etc.), oxycarbide (oxyxybibides) nitride, acid Nitride and the like can be used for at least one selected from non-metal oxide type or oxide capable of forming a glass phase.

In particular, the present invention is more preferably 3 to 10 parts by weight of at least one selected from alumina, silica, alumina-mullite, alumina-zirconia, but the particle size distribution at this time is 20 to 900nm (nanoparticles). The particle size distribution can improve the strength such that significant improvement can be achieved by improving the microstructure by ultrafine powder in order to increase resistance to infiltration and adhesion of molten steel. Therefore, in order to prevent the problem of loss due to re-adjustment of particle size, dissolution and oxidation of carbon in molten steel during use, and deterioration of strength in use, the product of product As a result of optimizing the microstructure, the physical properties and properties were improved significantly compared to the existing products.

At this time, the addition amount is 3 to 10 parts by weight is preferable, the improvement effect of the microstructure is not enough at 3 parts by weight or less, because at 10 parts by weight or more, it is a win-win of manufacturing. Nanoparticles are composed of alumina and silica, and their properties can be expressed with each or mixed components. The same effect is expressed in alumina-mullite and alumina-zirconia.

In using the nanoparticle roll, there is a problem that non-uniform mixing is caused by aggregation between particles at 20 nm or less, and the effect of improving the properties such as strength and corrosion resistance of the product is insufficient at 900 nm or more.

The preparation of nanoparticles can be achieved by grinding tens of microns of alumina, silica, and zirconia, respectively, into an grinding mill or from sol form.

On the other hand, the organic binder used in kneading is a resin of Rosol type or Novolac type, and therefore, Silicon Resin and Furan modified resin can be used.

The final chemical components prepared according to the raw material mixture of the present invention is 65 to 85 parts by weight of Al ₂ O ₃ , _{3 to} 14 parts by weight of ZrO ₂ , C 4 to 10 parts by weight and the rest 0.4 to 4 parts by weight of antioxidants and SiO _{2 and} SiC.

The following is described according to the embodiment.

Table 1 shows an example according to the present invention, densifying the tissue by firing or impregnation in a reducing atmosphere during production of the product. If necessary, it is calcined at low temperature (1000 ° C.) or prepared in an oxidizing or reducing atmosphere at high temperature (1400 ° C.).

      Table 1

～    Conventional              Embodiment of the present invention       One     2     3      4            Compound weight part ① Sintered or molten Al ₂ O ₃ (more than 90% of alumina)      50-90 Sintered or Electrolytic Al ₂ O ₃ (Alumina 97% or more) 1 to ₃ mm 38 Sintered or Electrolytic Al ₂ O ₃ (Alumina 97% or more) 1 to ₃ mm 37 Sintered or Electrolytic Al ₂ O ₃ (Alumina 97% or more) 1 to ₃ mm 45 Sintered or Electrolytic Al ₂ O ₃ (Alumina 97% or more) 1 to ₃ mm 20 Sintered or Electrolytic Al ₂ O ₃ (Alumina 97% or more) 1 ~ 0.04mm 28 Sintered or Electrolytic Al ₂ O ₃ (Alumina 97% or more) 1 ~ 0.04mm 20 Sintered or Electrolytic Al ₂ O ₃ (Alumina 97% or more) 1 ~ 0.04mm 30 Sintered or Electrolytic Al ₂ O ₃ (Alumina 97% or more) 1 ~ 0.04mm 30 ② Al ₂ O ₃ -SiO ₂ system, Al ₂ O ₃ -ZrO ₂ system, Al ₂ O ₃ -SiO ₂ -ZrO ₂ system    0-30 Sintered or Electrolytic Zirconia-Mullite 10 Sintered or Electrolytic Zirconia-Mullite 30 Sintered or Electrolytic Zirconia-Alumina 7 Sintered or Electrolytic Alumina-Zirconia 13 Sintered or Electrolytic Alumina-Zirconia 26 ③ Plasticized alumina (-1㎛, specific surface area over 3m ² / g) ① 5 to 20 of the ingredients      5      5      5     10  ④ Metal Si Fine Powder ② 4 to 10 sum with component carbon      One      One      2      3 ⑤ carbon (specific surface area 50m / g or more)    3 to 8      4      One      One      2.5 ⑥ Antioxidant metals (other than carbides)      -      4      One      One      0.5 ⑦ Nanocomposite particles Alumina 50nm 3 Silica 300nm 5 Zirconia 800nm 3 Alumina 30nm3, Silica40nm 5   Properties Porosity (%) 6 to 7      7     5     7      6 Volume specific gravity 2.9-3.1     3.1     3.2     3.3     3.4 Compressive strength (kg / cm ² )     -     2100    2860     300    3360 Thermal expansion rate (%) at 1000 ℃ +0.6 to 0.7       0.7      0.6       0.6      0.6 Chemical composition Al ₂ O ₃      79      74       85     83 ZrO ₂       7      11        4      8   C       8       5        5      7 Corrosion resistance with high frequency induction ★ (%) 1650 ℃ × 3hrs 100%     86%     75     70%     70% Oxidation Resistance (at 1000 × 3hr  100%     70%     70%      70%     70% Thermal shock resistance   usually     Great     Great     Great     Great  division  General steel STS steel grade, general steel General steel, general purpose General steel general purpose STS Steel General Steel Life expectancy (steel ladle)   3 to 4      6     7      9     10

★ Comparison of erosion area after 5 hours of erosion test

★★ Oxidation area and non-acid screen area after 3 hours at 1000 ℃ in electric furnace

★★★ The first cracking time occurred in the product by keeping the inside of the furnace at 1600 ℃ with the burner and then placing the product on the top.

As a result of the physical property test for Table 1, since the microstructure is not improved due to the addition of ultrafine powder, the mechanical strength is lower than about 1500kg / cm ^2, whereas the physical property is remarkably improved. And it was found.

Example 1

Compared with the conventional material, it can be seen that the application of ultrafine nanoparticles can improve the strength by improving the microstructure, and the chemical content is also significantly increased, and the oxidation resistance can be improved by about 30%.

Example 2

In the case of the present invention is intended to alleviate the problem of cracking in the long-term use as a product that applies only sintered or fully fused zirconia-mullite-based raw materials that are low-expandable minerals to improve heat spalling resistance.

Figure 3a is a micrograph showing the microstructure according to the present invention can be seen that the microstructure compared to the conventional micrograph shown in Figure 2a, Figure 3b is a photograph showing the appearance of the product after use of the present invention of the sliding portion While there is no melting loss in the refractory component, it can be seen that FIG.

Examples 3 and 4

This embodiment is a product that applies only sintered or molten alumina-zirconia raw materials to improve the thermal shock resistance and chemical content, and in particular, minimizes SiO ₂ to make it suitable for reducing steels, general steels and high Mn steels. to be.

The chemical composition of the sintered or premelted zirconia-mullite in the blended materials ranges from 40 to 46% Al ₂ O _3, 27 to 39% ZrO ₂ , and 15 to 20% SiO ₂ , and the content of ZrO ₂ is It is preferable to set it as 10 to 50% of range.

As described above, the present invention adds nanoparticles to prevent the loss of strength due to re-adjustment of particle size, dissolution and oxidation of carbon in molten steel during use, and deterioration of strength in use in the composition of raw materials causing the limitation of the service life of multiple times. As a result of optimizing the microstructure of the furnace product, it is possible to obtain the effect of improving the strength and increasing the content compared to the existing product.

Claims (3)

20 to 60 parts by weight of sintered (or electrolytic) alumina having a particle size of 1 to 3 mm, 15 to 45 parts by weight of sintered (or electrolytic) alumina having a particle size of 1 to 0.04 mm, 5 to 25 parts by weight of sintered (or electrolytic) zirconia-mullite Part, 5 to 25 parts by weight of sintered (or electrolytic) zirconia-alumina, 3 to 13 parts by weight of plastic alumina, 0.5 to 5 parts by weight of Si fine powder, 1 to 5 parts by weight of carbon, alumina, silica, alumina-mullite, alumina- Sliding plate refractory material, characterized in that it is mixed with 3 to 10 parts by weight and 0.3 to 5 parts by weight of antioxidant having at least one selected from zirconia 20 to 900 nm (nanoparticles). The method of claim 1, 5 to 50 parts by weight of the sintered (or molten) zirconia-mullite, 5 to 50 parts by weight of sintered (or molten) zirconia-mulite or sintered (or molten) alumina-zirconia instead of the sintered (or molten) zirconia-alumina Sliding plate refractory material characterized by using one or two selected. The method according to claim 1 or 2, According to the above formulation, the chemical composition is 65 to 85 parts by weight of Al ₂ O ₃ , _{3 to} 14 parts by weight of ZrO ₂ , 4 to 10 parts by weight of C, and the rest consists of 0.4 to 4 parts by weight of antioxidant and SiO _2, SiC. Sliding plate fireproof material.

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