JPS59169978A - Porous plag - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention relates to a bosis plug for blowing gas that is attached to a molten metal container such as a ladle or tundish for stirring M steel or floating and removing inclusions in molten steel. It is something.

Currently, in the steel manufacturing process VC, a process of blowing gas through a refractory is commonly used for the purpose of improving surface quality, corrosion resistance, hot workability, etc. of steel, and upgrading alloy steel. This method involves completely stirring the molten steel at °C by gas injection to make the molten steel temperature uniform, or by bubbling fine bubbles to eliminate inclusions such as CrQO11, Ae208, titanium oxide, mankan silicate, etc. The purpose is to achieve the above objective by floating and releasing the gas, and the gas injected here is mainly inert gas such as Ar or N2 gas, but in the ladle smelting furnace, Ar and 02 gas are Degassing and decarburization are performed by blowing a mixed gas of

After being used for gas injection, the porous plug is cleaned with oxygen by spraying it with oxygen gas through a sharp lance in order to remove all the attached metal. In such a case, the temperature of the molten metal or the porous plug becomes very high, and the porous plug, which is a porous refractory, is likely to be damaged. Therefore, the porous plug must be made of a refractory material that has particularly excellent corrosion resistance against oxygen gas.

Conventionally, alumina materials have been mainly used for this type of porous plug, but because the aggregate particles are non-spherical, there are a number of problems during the manufacturing process or the porous plug itself: (1) During mixing, kneading, and molding, the particles The edges of the mold are crushed or destroyed, and the particle size distribution changes (2) Due to internal friction between the kneading lamps and interfacial friction between the clay and the mold, a non-uniform filling structure results.

(3) The shape of the pores is irregular; (4) the air permeability is low; (5) it is difficult to obtain the desired physical properties, such as air permeability, pore density, and porosity; Because of problems such as the occurrence of ffl orientation, it is difficult to maintain the process integrity and quality of the manufacturing process.

In order to overcome these drawbacks, a method using spherical particles has been reported. For example, Utsukai 51-
The technical matter disclosed in No. 157570 uses mullite spherical particles, but the mullite spheres are 5102
Because of its high content, it not only has poor corrosion resistance against molten steel, but also has extremely low resistance to convergent gases such as oxygen cleaning. It is occurring.

In addition, the air permeability, which is a characteristic that a porous plug should have, is approximately 0.5 to 3 CCC-tyn/cpA-sea.
avH20), and when trying to obtain an air permeability of 1.0 or more, the general manufacturing method is to mold at a low molding pressure. Therefore, the strength of the compact is naturally low, and handling up to firing is extremely difficult, and the corrosion resistance is also poor.

In view of the current situation, the present invention was made with the aim of proposing a porous plug for gas injection that achieves the desired air permeability and uniform structure, has excellent IT resistance and thermal shock resistance, and provides specific details. The purpose of the present invention is to provide a △ porous plug using alumina spherical particles that have excellent corrosion resistance, flexibility, and particle strength.

The porous plug of the present invention will be explained below.

First, as a result of studying how to improve the corrosion resistance of spherical particles,
Regarding the chemical composition of the individual particles, Al2O8 is 89wt%.
As described above, it has been confirmed that S i O2 of 11 wt% or more is a condition that satisfies corrosion resistance as a refractory material forming a porous refractory. Next, we examined the resistance to oxygen gas and found that the temperature during oxygen cleaning reached approximately 2000°C, and as a result, the above composition content of SiO2 caused significant erosion, and corrosion resistance was not achieved unless the SiO2 content was kept below approximately 11%. It turned out that maintenance could not be maintained for 1 hour after the initial period.

Next, various examples will be given based on this knowledge.

Commercially available sintered alumina, zircon, or chromium oxide were blended in the ratios shown in Table 81, a phenol resin was added, and the mixture was optically kneaded in a fret mill, then molded in an oil press, dried, and fired.

7 Yarn 1 is a conventional product that uses non-spherical particles as aggregate particles.
5 (10kg 7c) to maintain a specified amount of breathability
It was molded at a molding pressure of d.

&2 to 14 are products of the present invention, using alumina spherical particles as aggregate, molded at a molding pressure of 1000 and 9/d,
After drying, it was fired at 1700°C for 6 hours.

The properties of the porous refractories obtained are also shown in Table 1.

The composition or blending ratio on the wood surface is wt%, and each test method was performed as follows.

The melting loss ratio @) was calculated by blowing oxygen gas into each fired body using a sharp lance, performing an oxygen cleaning test at 2000°C for 10 minutes, and measuring the melting loss by 4'N dll.
6. It is shown as the melting loss rate when (l+j is 100 (correspondence)) of 1.

For 7ff without cracking, 40 x 40 x
A 401N+ specimen was heated to 1500'C in an electric
The procedure was repeated as follows: 1), hold it for 20 minutes, then take it out and let it cool. Depending on the number of operations and the condition of the cracks, after 2 times, there will be no cracks. ◎ After 1 time, there will be no cracks. After 01 times, slight cracks will occur.
...After 61 times, a large crack appeared...Pa...
Thermal shock resistance was verified as ×.

The aggregate particles of Nos. 1 to 10 and Nos. 12 to 14 have a particle size of 0.
84~0.59 printing occupancy is 2 to 3Q wt, 51
1 has a particle diameter of 084 to 0.5!lff, which accounts for about 4rlyt, and an occupancy of 0.591 to o, and smt, which accounts for about 35 ivt%.

From the results shown in Table 1, as the amount of finely powdered alumina added increases, the n1 porosity, pore size and air permeability decrease, and the reverse porosity improves. -1: Thermal shock resistance tends to deteriorate as the amount of fine alumina increases.

Inferring from this, for a highly corrosion-resistant porous plug with a small content of 5 in2, the suitable amount of fine powder alumina powder to be added is approximately 15 wt%.
It can be seen that if the configuration is within this range, the air permeability and thermal shock resistance will be the same or better than the conventional product with a rating of 1, and the corrosion resistance of 6 will be extremely superior. .

The reason why the product of the present invention has higher corrosion resistance than the conventional product is thought to be due to the degree of sintering and the interparticle spacing caused by the molding pressure. In other words, while using non-spherical particles like conventional products! If air permeability is to be improved, the molding pressure must be lowered or coarse particles must be used. When the particle size is increased, the ridges of the particles are ground during mixing, cross-wiring, and molding as described above, and the particle size distribution tends to fluctuate, so it is generally easier to manage physical properties by lowering the molding pressure. When the molding pressure is lowered, the particle coordination becomes sparse and the gaps become extremely large, making it difficult to sinter.

In other words, the strength of A1 is mainly due to the mere mechanical strength due to crystal shape complexity, and the penetration of molten mackerel is easily reduced due to insufficient sintering or bonding between particles. It will be solved.

No fEh 7 to 10 are those in which f) VC zircon powder is added instead of fine powder alumina, and when compared with Nos. 2 to 6, the strength and thermal shock resistance are similar, but it is difficult to expect an improvement in corrosion resistance. This is thought to be due to the amount of sio□ contained in the zircon shell. On each side, the zircon powder pot with an inclination of &7 to 91 is about 10
．． If the content is limited to 0 Wtq6, excellent corrosion resistance can be obtained.

1i 11 is a product in which the particle size distribution of alumina spherical particles is expanded to the larger particle size, and the interparticle bonding is performed using alumina and zircon fine powder, but it has better air permeability and corrosion resistance than conventional products. The results also showed excellent thermal shock resistance.

Black 12 to 14 are those in which the content of chromium oxide was further studied for the purpose of corrosion resistance. As the chromium oxide content increases, corrosion resistance improves, while strength and thermal shock resistance deteriorate7. Therefore, the preferred content is approximately 2 wt% or less.

Summarizing the above results, in contrast to the conventional product that uses all non-spherical particles as aggregate, alumina spherical particles with a controlled chemical composition of single particles are used as aggregate: + The invented product has excellent air barrier properties, corrosion resistance, and thermal shock properties. It was confirmed that the desired air permeability can be obtained by selectively changing the mass of the added fine powder even when the molding pressure is high.

As can be seen from the above description, the horus plug of the present invention exhibits an excellent effect when attached to a molten metal container such as a ladle or dish/dish. The idea is not limited to the above examples, and any applications, diversions, or modifications derived therefrom are not necessarily included in the technical scope of the present invention.

Claims (1)

[Claims] ■From 1 refractory @ material in which the chemical composition of the 9-particle funnel is 891% t% or more of Al2O8, 11wt% or less of 5102, and the aggregate is spherical or thin alumina spherical particles. Porus Gelag is characterized by: 2. In the refractory material according to claim 1, the alumina spherical particles with a particle size of 2.0 to OJa are
owts or 0 to 2 wt of chromium oxide with a particle size of 20μ or less
A porous tin rag characterized by a particle size distribution consisting of % and a composition with a good composition.