CN1060752C - Production method of refractory material for immersed sprue - Google Patents

Abstract

The invention relates to a method for manufacturing a carbon composite refractory material for a submerged nozzle for continuous casting, which is composed of a nozzle body and an anti-clogging composite layer inside. Magnesia-aluminum spinel and sintering aids are mixed and formed by isostatic pressing, and sintered into ceramic composite sand at 1500-1750°C in a non-oxidizing atmosphere, and composite sand: 25-45%, stabilized zirconia: 20- 35%, natural flake graphite: 10-15%, phenolic resin: 5-8%, Alon: 5-10% After mixing and grinding, compound with the nozzle body, form by isostatic pressing and sinter.

Description

A method for manufacturing a submerged nozzle refractory material

The invention relates to a method for manufacturing a refractory material, especially a method for manufacturing a submerged nozzle with a thin wall that can prevent the deposition of Al ₂ O ₃ .

Preventing Al ₂ O ₃ deposition or clogging at the submerged nozzle for continuous casting _{is an} inevitable requirement for _the stability _of the continuous casting process _. As a result of the reaction of Al in molten steel and deposition on the inner wall of the nozzle (i.e. nozzle nodulation), this blockage is an unsolved problem no matter for general continuous casting or thin slab continuous casting. In the prior art, there are mainly the following solutions plan:

1. Air blowing type multi-layer structure is adopted, which is the most commonly used method for resisting Al ₂ O ₃ deposition at present, and the structure of the nozzle is complex. For thin slab continuous casting, since the wall of the thin-walled nozzle itself is very thin, it is obviously impossible to adopt this structure.

2. Nozzle insulation, Al ₂ O ₃ precipitation is due to the temperature drop of molten steel, and the Al in the steel reaches a saturated state to create conditions for Al ₂ O ₃ precipitation. The outer wall of the nozzle is covered with a ceramic fiber layer to reduce the heat loss of molten steel in the submerged nozzle. , which is beneficial to resist Al ₂ O ₃ deposition. After all, this is an auxiliary method. For thin slab continuous casting, this measure is also limited by thin walls.

3. The material of the inner wall of the nozzle is improved, and the material that reacts with the attached Al ₂ O ₃ to form a low-melt material is selected. The low-melt material can be washed away by molten steel, which can prevent Al ₂ O ₃ from clogging. Japanese Patent Laying-Open No. 57-71860, 62-288161, and Japanese Patent Laid-Open No. 4-224061 all proposed the method of introducing CaO into the nozzle material, that is, selecting CaO-ZrO ₂ -C series materials to form Al ₂ O ₃ -CaO- ZrO ₂ is a low-soluble substance to prevent the deposition of Al ₂ O ₃ . The content of CaO in this type of technical material is high, and the raw materials and products are easy to hydrate and disintegrate. Chinese patent CN1112909A discloses a nozzle material that prevents Al ₂ O ₃ deposition and clogging, that is, calcium fluoride is added to the ZrO ₂ -C material, which is to achieve anti-Al ₂ O ₃ at the cost of partly sacrificing the life of the nozzle. For the purpose of deposition, it is obviously not suitable to use the melting loss method for the thin-walled nozzle whose wall itself is not thick.

U.S. Patent 4804644 discloses a "ceramic material", which is isostatically pressed by zircon, silicon nitride, alumina and sintering aids such as yttrium oxide or magnesium aluminum spinel, and then sintered at 1500-1750 ° C , the ZrO ₂ ceramic material is evenly distributed in the O′-Sialon matrix. The material has excellent anti-AL ₂ O ₃ deposition performance, but poor anti-erosion and anti-steel erosion resistance, and cannot adapt to the technological requirements of thin-walled nozzles.

The object of the present invention is to obtain a manufacturing method of a submerged nozzle refractory material, which has poor reactivity with Al ₂ O ₃ , small combination, and strong resistance to molten steel erosion and erosion.

The purpose of the present invention is achieved like this:

A method for manufacturing a submerged nozzle refractory material, which is composed of two parts: the nozzle body and the anti-clogging composite layer inside the nozzle. The manufacturing method of the anti-clogging composite layer is: use zircon, silicon nitride, magnesium aluminum Spinel and sintering aids are used as raw materials, after mixing, they are formed by isostatic pressing, fired into ceramic composite sand in a non-oxidizing atmosphere at 1500-1750°C, crushed and sieved into required particle size specifications, and According to the following ingredients (weight): composite sand: 25-45%, stabilized zirconia: 20-35%, natural flake graphite: 10-25%, phenolic resin: 5-8%, Alon or Alon: 5-10 %, after mixing and milling the mud, it is compounded with the nozzle body, formed by isostatic pressing and then sintered to make the required submerged nozzle.

The raw material composition (weight) for making composite sand is: zircon: 35-55%, silicon nitride: 20-50%, magnesium aluminum spinel: 10-20%, sintering aid: 2-8%.

The sintering aid is any one of yttrium oxide, aluminum oxide, magnesium oxide, calcium oxide, and silicon oxide or any combination of the above additives.

The present invention is described in further detail below.

The composite sand manufactured by the present invention is made of zircon, silicon nitride, magnesia-alumina spinel, and three kinds of materials with sintering aids added as raw materials. The content and effect of each component are as follows:

Zircon: 35-55% (weight percentage, the same below), which can improve the corrosion resistance of the material, if it is too high, the anti- _Al2O3 deposition will be deteriorated, and it will easily cause overburning during sintering, and if it _is too low, it will cause Low density during sintering.

Silicon nitride: 20-50%, reacts with zircon as follows:

Si ₂ N ₂ O reacts with Al ₂ O ₃ to obtain O'-Sialon. The obtained O'-Sialon has the characteristics of anti-Al ₂ O ₃ deposition and poor wettability with molten steel. It forms a liquid phase at high temperatures above 1550-1600 °C film, making Al ₂ O ₃ attachment difficult.

Magnesium-aluminum spinel: 10-20%. The invention also adds finely dispersed magnesium-aluminum spinel, part of which is used as a sintering aid, and the other part exists in the matrix as an independent phase, which can improve the corrosion resistance of the material.

Sintering aid: 2-8%, one of yttrium oxide, aluminum oxide, calcium oxide, silicon oxide or any combination of the above additives.

Mix the above raw materials and grind the mud, form it by isostatic pressing, and fire the ceramic material in a non-oxidizing atmosphere at 1500-1750 ° C. It is a kind of ceramic material that has little reactivity with Al ₂ O ₃ and poor wettability with molten steel. Ceramic material with strong corrosion resistance, its main phase composition is: O'-Sialon, magnesium aluminum spinel, stabilized zirconia and high viscosity glass phase, after crushing and screening to make ceramic composite sand, use the composite sand The anti-clogging layer carbon composite material on the inner wall of the nozzle is made of other raw materials, and its composition is (percentage by weight): composite sand: 30-50%, stabilized zirconia: 20-40%, natural flake graphite: 10-25%, phenolic Resin: 5-8%, Alon: 5-10%. After the above raw materials are mixed and crushed, they are combined with aluminum carbon and zirconium carbon nozzle body, formed by isostatic pressing and sintered to make a submerged nozzle. The function of each component is:

Composite sand: 25-45%, (weight percentage, the same below), due to the presence of O'-Sialon, cubic zirconia _ZrO2 and magnesium-aluminum spinel phases in the composite sand, the needle-like crystals of O'-Sialon are interlaced and formed A braided structure, ZrO ₂ and magnesium aluminum spinel particles are mainly filled in the control gap of the braided structure to play a role of dispersion strengthening, so the material has excellent mechanical properties. At high temperature, a high-viscosity liquid phase film is formed on the surface of molten steel and composite sand to hinder the deposition of Al ₂ O ₃ , while the magnesium-aluminum spinel phase can improve the corrosion resistance of the material.

Stabilized zirconia: 20-35%, forming cubic zirconia to improve the corrosion resistance of the material, if it is too high, the resistance to Al ₂ O ₃ deposition will deteriorate, and if it is too low, the corrosion resistance will decrease.

Natural flake graphite: 10-25%, to improve the thermal shock resistance and erosion resistance of molten steel.

Phenolic resin: 5-8%, the binder during pressing and forming, if it is too low, the wettability of the mud material is poor, and the strength of the green body is poor; if it is too high, the volatile content of the mud material is high, and the green body is prone to cracks.

Alon: 5-10%, good high temperature stability, can replace part of O'-Sialon, improve the material's resistance to erosion and thermal shock, if it is too low, it will not work, if it is too high, the cost will be too high.

After the above raw materials are mixed and muddyed, they are combined with the nozzle body of aluminum carbon and zirconium carbon materials, formed by isostatic pressing, and then sintered to make the submerged nozzle.

Embodiments of the present invention are described below in combination with effects.

The following raw materials are used: zircon, silicon nitride, magnesium aluminum spinel, wherein the composition of magnesium aluminum spinel is (weight percent): MgO: 30%, Al ₂ O ₃ : 67%, SiO ₂ : 2.5%. 0%, CaO: 0.5%, Fe ₂ O ₃ : 0.5%, the chemical composition of raw materials is shown in Table 1.

Grind all the raw materials to be below 7 μm. The specific ratio is shown in Table 2. Put them in a ceramic ball mill according to the required ratio, use alumina balls as the grinding medium, add alcohol and wet mix for half an hour to make the raw materials mix evenly, and then dry , Grind and set aside.

The mixed raw materials are first placed in a steel mold and pre-compressed with an axial pressure of 30 MPa, and then cold isostatic pressed with a pressure of 200 MPa on a cold isostatic press. In a resistance furnace, sinter at 1600°C under argon protection for 3 hours to obtain ceramic composite sand. The composite sand is crushed and sieved into the required particle size, and the following components are: composite sand: 30%, stabilized zirconia: 40%, Natural flake graphite: 17%, phenolic resin: 5%, Alon: 8%. After mixing and grinding the mud, the specific composition of the anti-clogging composite layer inside the nozzle is shown in Table 4. After compounding with the aluminum carbon material nozzle body, the pressure is 250-300MPa Cold isostatic pressing, sintering at 1150-1200°C for 24 hours to make submerged nozzle. The Al ₂ O ₃ deposition resistance test was carried out on the anti-clogging composite layer, and the results are shown in Table 5. Test conditions: induction furnace at 1600°C for 1 hour, the upper layer is mold slag, the lower part is molten steel, and the chemical composition of molten steel is (killed steel): C: 0.15, Si<0.03, Mn: 0.4, P : 0.008, S: 0.012, Al: 0.051.

The results of energy spectrum analysis show that there is almost no Al ₂ O ₃ on the hot surface of the material of the present invention and the O'-ZrO ₂ -C material, indicating that Al in molten steel cannot be deposited on the surface of the material. Compared with the prior art, the material of the present invention adds magnesium-aluminum spinel with strong erosion resistance, so that part of the magnesium-aluminum spinel is used as a sintering aid and a part exists as an independent phase. Therefore, the present invention The corrosion resistance of the material is stronger than that of O'-ZrO ₂ -C material. The material not only has good anti-Al ₂ O ₃ deposition performance, but also has good anti-erosion and scour ability of molten steel.

Table 1 raw material N Si Free Si _ZrO2 Al ₂ O ₃ SiO _{2 Fe2O3 _} TiO ₂ R ₂ O CaO MgO Si ₃ N ₄ 38.07 57.11 1.7 ZrSiO ₄ 64.68 <0.10 33.60 0.12 0.06 0.072 0.012 Al ₂ O ₃ 98.78 0.08 Trace 0.04 / / SiO ₂ 0.40 98.19 0.04 0.06 0.23 0.18 0.09

Table 2

table 3

Table 4

table 5 Materials of the invention CaO-ZrO ₂ -C material O′-ZrO ₂ -C material Anti-Al ₂ O ₃ Deposition Index 1.8 2.0 1.8 Slag corrosion resistance (mm) 0.020 0.020 0.048 Anti-melting steel corrosion (mm/min) 0.015 0.015 0.021

Claims (1)

1. the manufacture method of a refractory material for immersed sprue, be that anti-clogging plug composite bed two portions by mouth of a river body and inside, the mouth of a river are composited, it is characterized in that: the manufacture method of anti-clogging plug layer is: the raw material of using following ingredients (weight): zircon: 35-55%, silicon nitride: 20-50%, magnesium-aluminium spinel: 10-20%, the sintering aid yttrium oxide, aluminum oxide, magnesium oxide, calcium oxide, the arbitrary combination of any in the silicon oxide or above additive: 2-8%, isostatic pressing behind mixing, in 1500-1750 ℃ of Low fire ceramic complex sand in non-oxidizing atmosphere, with this complex sand fragmentation, sieve into the desired particle size specification, and by following composition (weight): complex sand: 25-45%, stable zirconium oxide: 20-35%, natural flake graphite: 10-25%, resol: 5-8%, A Long are Alon:5-10%, after mixing grinds mud, with this volume recombination of the mouth of a river, with behind the hydrostatic pressing at 1150-1200 ℃ of sintering, promptly can be made into required submerged nozzle.