JPH03159956A - Production of porous refractory for gas blowing - Google Patents

Abstract

PURPOSE:To obtain the subject porous refractory for gas blowing, having excellent spalling resistance, gas permeability, etc., by molding a mixture of magnesia as a main material containing specific amounts of titanium dioxide and fine alumina and sintering. CONSTITUTION:(A) 0.3-10wt.% titanium dioxide of rutile structure and (or) anatase structure is blended with (B) 0.4-15wt.% alumina having <=100mum average particle diameter and (C) the rest of magnesia. Then the prepared mixture of magnesia as a main material is molded and then sintered to give porous refractory for gas blowing. Further blending of <=10wt.% one or more selected from compounds containing cations of Si<4+>, Zr<4+>, Fe<3+>, Mg<2+>, Li<+>, Ni<2+> and Cr<2>+ having the same or larger diameter of cation than that of titanium can prevent reduction in corrosion resistance caused by addition of titanium dioxide.

Description

DETAILED DESCRIPTION OF THE INVENTION = 1 [Industrial Field of Application 1] The present invention relates to a method for producing a gas-blown river refractory having excellent river resistance.

[Prior art] Inert gas is blown into molten metal using a porous plug for the purpose of adjusting the temperature of molten metal, making the composition uniform, removing non-gold H tailing compounds, etc. In addition, in the nozzle for molten #l casting, inert wI. It is known to blow in scum (for example, when the
Publication No. 34342, Act. JP-A-53-128317, JP-A-56-148453).

The material of the porous refractory used for this gas blowing is mainly alumina (for example, JP-A-50-45
Publication No. 810).

[Problems to be Solved by the Invention] Algina refractories are excellent in ml/1 corrosion resistance and spalling resistance. However, when used as a porous refractory for gas blowing, the cooling effect of the inert gas creates a significant temperature difference between the contact surface and the molten steel, and even aluminum refractories can avoid damage due to spalling. It is not possible. When cracks occur due to spalling, gas permeability decreases due to the intrusion of molten steel, and if the cracks are large, this can lead to major accidents such as leakage of hot water.

Siliceous materials such as fused silica with a small coefficient of thermal expansion
Alternatively, it is known to add carbon powder, which has the effect of absorbing thermal expansion, to improve the spalling resistance pτ. However, if sufficient effects cannot be obtained with either method,
For siliceous raw materials, the additive is
1x has low corrosion resistance. - On the other hand, carbon powder blocks pores and reduces gas permeability.

The object of the present invention is to provide a porous refractory for slag blowing that does not have the following disadvantages.

[Means for Solving the Problems] The present invention provides th! Titanium dioxide 0.3-1 in jk ratio
0% and l/alumina with a uniform diameter of 100 llm or less 0.4~
15w+%. After molding the compound where the remainder is mainly magnesia,
This is a manufacturing method for gas-blown porous refractories characterized by firing.

The present invention will be explained in more detail below.

The titanium di-diluted material used in the present invention is, for example, Ilmenai 1
・It is produced by refining, firing, and crushing the raw material 1'. Due to its concealing power, youthful color power, and insoluble edict properties, it has traditionally been used as a coating of 1+. Ink, paper, plastic fillers, porcelain raw materials, abrasive materials, porcelain products, etc.
It is widely used in various products, and it can also be obtained from commercially available products.

Titanium dioxide is known to be of the rutile type and the anatase type, and both forms can be used in the present invention.

In order to achieve the effect even when added in a small amount, the particle size should be adjusted to an average particle size of, for example, from n4 μIll to Q) fine'+-7. It is strange to use /-.

The addition ratio of titanium oxide in the inclusion is heavy
;'PI 0.3-10% 6. 0.
+i%J 91! l Te (1; l: Ill There is no effect on spalling properties, and if it exceeds 10%, the strength will decrease and the corrosion resistance will be poor. The most favorable range is 0.5 to 5%.

The reason why the addition of titanium dioxide in the present invention improves the spalling properties of porous porous materials is believed to be due to the following rationale. That is, titanium oxide is used at t/f in manufacturing of large porous objects. In the Ily process, it reacts with the alumina component in the refractory material, producing aluminum titanate in the matrix. When this aluminum titanate is observed under a microscope after firing, it is confirmed that there are cracks in the grain boundaries of the aluminum titanate. The 11' increase in ml·I spalling property is thought to be due to the absorption of thermal stress by cracks in the crystal grain boundaries. Therefore, in combination with a refractory material that does not have an alumina component, aluminum titanate does not grow, and the effects of the present invention cannot be obtained.

Magnesia as the main aggregate may be either a fired product or an electrofused product. From an economic point of view, it is desirable to use the power of inexpensive sintered products. 1'1'I. The particle shape may be either a 1% particle or a spherical particle.The particle size is, for example, one with a small intermediate diameter so as to obtain a porous structure.

(Cracks in the grain boundaries of aluminum titanate are effective in improving the spatter resistance.)Also, as the amount of titanium dioxide added increases, the splintering resistance tends to decrease, perhaps because it lowers the mechanical strength. It will be done. To solve this problem, it is necessary to use Si'', Zr'', and ゛(・゜,
It is preferable to add one or more cations selected from the following compounds: Mg'', l.i'', Ni'' or Cr'+.

This is because these compounds or the titanium cation '1'-
By having cations equal to or larger than the diameter, it forms a solid solution with aluminum titanate produced during firing of porous refractories, suppresses the formation of aluminum titanate crystals, and suppresses the formation of aluminum titanate crystals. 'u'll''lVILfkomust・BL
It seems that this is to prevent rl, 1 Specific examples of these compounds include, for example, SiO, M)<0
, Fo,03, Cr, 0,, Nip, Lid.
There is ZrO. The particle size of these compounds is not particularly limited, but in order to reduce the reactivity, it is preferable to use finely milled or AI-like particles.
Let Il be de. When these compounds are added, their proportion in the formulation should be 10% or less on a weight basis. 1
If it exceeds 0%, the occurrence of cracks at the grain boundaries of aluminum titanate is too suppressed, so that the effect of improving spalling resistance (1) cannot be obtained. In addition, if you try to obtain the effect by adding these compounds in 1 min, it will be more than 1% J'. Is it necessary to add fA?

Below 1-. In addition, in the present invention, additives such as refractory aggregate, metal powder, clay, etc. known in the production of porous refractories may be added to the extent that they do not impede the effects of the present invention.

For shaping, an inorganic or organic binder is added in an amount of about 1 to 5% by weight based on the entire mixture, and after cross-mixing, it is pressed into an arbitrary shape.

The firing temperature is preferably 1300 to 1800°C. ．． [Example] Examples of the present invention and comparative examples thereof are shown below.

Table 1 shows the quality of the titanium dioxide used in each example.

Table 2 shows the compounding composition of each example and the test results of the bolus refractories produced therefrom.

In each example, in order to obtain a porous refractory structure, a blending composition was used in which the amount of intermediate-diameter bone phase particles was reduced compared to that of a normal refractory. In addition, calcium lignin sulfonate is added as a binder to the molding process in a state dissolved in water.
Pressure was applied using a friction press. Firing at 1700℃
I went there in 6 hours.

The test method is as follows.

Porosity: Measured according to JIS-R2205.

7 Compressive strength - Measured according to JIS-R2206.

Air permeability: illU constant with room temperature air.

- Spalling property 30 x 40 x 120n+m
The test piece was heated in an electric furnace for 30 minutes, then cooled in the air, and this process was repeated to determine f (the number of times until four cracks occurred).

Erosion resistance - Measured by rotary erosion test using a steel piece as an eroding agent. After repeating 1650"C x 30 minutes 3 11+1 times, the erosion dimension was measured and expressed as an index with the erosion dimension of the refractory of Comparative Example 5 as 100. The smaller the value, the better the corrosion resistance. A porous plug and a "YUNOSUL" for sliding nozzles were manufactured, and the porous plug was installed in a 3001 molten steel ladle, the upper nozzle was installed in a 60 furnace, and a tundish, and the durable M number was determined by iota. In the table, blank data are unused.

8-71 All of the examples of the present invention are excellent in spalling resistance. Among Examples 8 to 10 of the present invention, in addition to spalling resistance, corrosion resistance was excellent, and in an actual machine test using a porous sp top nozzle, the service life was further improved compared to Examples 1 to 2.

Comparative Example 2, in which too much titanium dioxide was added, had poor corrosion resistance. Comparative Examples 3 and 4, in which the amounts of magnesia powder and chromium oxide added are too large, are inferior in the spalling properties.

〔effect〕

As is clear from the test results of the above examples, the porous refractory obtained by the present invention exhibits excellent spalling resistance even against the significant temperature difference experienced during gas injection. Moreover, corrosion resistance and gas permeability are not impaired. Therefore, there is no need to worry about major accidents such as leakage of hot water, and functions such as stirring molten steel by blowing gas and preventing nozzle clogging can be fully performed depending on the application.

Claims (3)

[Claims] (1) Gas blowing characterized by molding a mixture of 0.3 to 10% titanium dioxide, 0.4 to 15% alumina with an average diameter of 100 μm or less, and the balance mainly consisting of magnesia, and then firing it. Method for manufacturing porous refractories for use. (2) Titanium dioxide 0.3-10% by weight, alumina 0.4-15% with an average diameter of 100 μm or less, Si^4^+ whose ionic radius is equal to or smaller than the radius of the titanium cation; Zr^4^+, Fe^3^+, Mg^
2^+, Li^+, Ni^2^+Sl^3^+ or C
A method for producing a porous refractory for gas blowing, characterized in that a compound containing 10% or less of one or more selected from compounds having an r^3^+ cation and the remainder being magnesia is molded and then fired. (3) The method for producing a porous refractory for gas blowing according to claim 1 or 2, wherein the titanium dioxide is of rutile type and/or anatase type.